Early Labor
The birth process begins with early labor. Early labor is part of the first stage of labor, which ends when the cervix--the tissue separating the vagina from the uterus--is dilated to 10 centimeters. The early stage of labor consists of mild, minimally uncomfortable contractions of the uterus occurring every 5 to 20 minutes lasting 30 to 60 seconds, the Mayo Clinic says. The contractions of early labor thin the cervix and begin to dilate, or open, it. Early labor is usually the longest part of labor, lasting an average of 8.5 hours in women having their first baby and five hours in subsequent pregnancies.
Active Labor
Active labor is the next part of the first stage of labor. During this stage, the cervix dilates to a full 10 centimeters; contractions become more intense and painful, and they occur every three to four minutes with a duration of 40 to 60 seconds, according to the Palo Alto Medical Foundation. The amniotic sac--the fluid-filled bag surrounding the baby--often breaks spontaneously during this stage of labor. Physicians sometimes break the bag of water to speed labor. Transition is the period of dilation from 7 centimeters to 10 centimeters. Women often have an urge to push during this stage, even though the cervix isn't fully dilated yet. Pushing too soon can make the cervix swell, which increases the time needed for dilation. Transition is considered the hardest part of labor but also the shortest, lasting 30 minutes to two hours.
Second Stage Labor
Once the cervix has dilated 10 centimeters, second stage labor begins. The baby begins to descend through the cervix into the vagina. Pushing with the contractions facilitates the baby's movement. This stage may take an hour or more, especially in women having their first baby or those who have had epidural anesthesia, which decreases the pushing reflex. Eventually, the baby's head will "crown" or appear at the vaginal opening. Women who've already had one baby may push only 15 to 30 minutes; sometimes they push only once.
The fetal position may influence the length of second stage labor. Babies whose heads face toward the front of the mother's pelvis, a position known as occiput (meaning head) posterior, take longer to navigate the birth canal. Most babies are born face-down. Once the head is delivered, the shoulders rotate so they can slide under the pubic bone one at a time. In most babies, the head circumference is the largest part of the body. Some babies, especially those who are macrosomic or larger than normal, may have shoulders wider than the head. These babies may have shoulder dystocia, in which the head is delivered but the larger shoulders get stuck. Shoulder dystocia can be a medical emergency because the baby's oxygen supply is compromised, the Merck Manual says.
Third Stage Labor
The third stage of labor is the delivery of the placenta. Though it lacks the drama of the actual delivery, delivery of the placenta--the organ that supplied nutrients to the baby during pregnancy--is necessary. A placenta that doesn't make an appearance within 30 minutes is a concern and may need to be manually removed.
